GEOLOGY OF LAKE PLEASANT QUADRANGLE 33 



In 1893 Darton ^ made a generalized structure section across 

 the valley at Wells and made some brief statements regarding the 

 outlier. 



In 1897 and 1898 Ruedemannr in presenting arguments for the 

 existence of an Ordovicic ocean current, referred to the Wells out- 

 lier in his second paper expressing his belief that the Paleozoic 

 strata of the outlier occupy a fault valley or " graben " and that 

 the strata originally belonged to a continuous mantle of sediments 

 which covered the southern Adirondack region. Neither map nor 

 structure section were presented by Ruedemann. 



The only detailed study of this outlier heretofore presented is 

 by Kemp, Newland and Hill in 1898.^ Alany important points are 

 brought out in this paper (see references below) but, since the 

 Lake Pleasant sheet was not then published, a sketch map only, 

 showing the principal outcrops of Paleozoic rocks, accompanied the 

 report. No structure section was attempted. 



During the summer of 1912 the writer made a very detailed 

 survey of the vicinity of Wells and as a result of this work data 

 were obtained for the preparation of the first detailed areal geological 

 map of this outlier, published in connection with this bulletin. 

 The accompanying structure sections across the valley at Wells are 

 also the first to be based upon a detailed survey. 



Of all the known outliers in the southern Adirondacks, the most 

 complete Paleozoic section is shown in this one at Wells, the fol- 

 lowing formations all being well represented : Potsdam sandstone ; 

 Theresa transition beds; Little Falls dolomite; Lowville limestone; 

 Trenton limestone; and Canajoharie (Trenton) shale. The section 

 is not perfectly continuous but, as nearly as can be determined, 

 the total thickness of the Paleozoic strata lies between 486 and 564 

 feet, with 500 feet probably close to the actual thickness. 



As shown on the accompanying sketch, the strata comprise 

 an inverted V-shaped area of rocks bounded on each side by a 

 prominent fault with a minor fault parallel to the major ones passing 

 through the village of Wells. These faults are described in a suc- 

 ceeding chapter. The greatest length of the outlier is 4^ miles 

 along the western side; its greatest width is i^ miles through the 

 village ; while its area is a little over 3 square miles. 



1 13th Annual Rep't, etc., N. Y. State Geol. for 1893, p. 608-9. 



2 Amer. Geol., June 1897; Amer. Geol., Feb. 1898. p. 75. 



3 i8th Annual Rep't N. Y. State Geol., 1898, p. 145-52. 



